I'm using the F5 Networks Big-IP products, which are appending a custom Ethernet II trailer frame for debugging purposes. I'm trying with Scapy to bind a new layer for this trailer, but I'm unable to do so.
I can see the payload of interest in the Padding field but using bind_layers does not perform proper dissection of the required Padding section.
class MyEthTrailer(Packet): name = "Ethernet Trailer" fields_desc = [ ####Fields Mapping Section ] def dissect(self, s): self.payl,self.pad = self.extract_padding(s) s = self.do_dissect(self.pad) One solution I was thinking was to create a new Ethernet replacement class (or overloaded), which I can then refers to the typical Ethernet payload and my new trailer. But I'm not a super Python/scapy programmer, and I am not certain if this is the best option.
This is how Scapy currently maps my packet after I apply bind_layers(TCP,MyEthTrailer). The info I should have parse is in the Padding class
<Ether dst=00:00:00:00:00:00 src=00:00:00:00:00:01 type=0x8100 |<Dot1Q prio=0L id=0L vlan=01L type=0x800 |<IP version=4L ihl=5L tos=0x0 len=67 id=1 flags=DF frag=0L ttl=255 proto=tcp chksum=0x01 src=10.0.0.1 dst=10.0.1.1 options=[] |<TCP sport=1111 dport=https seq=1 ack=1 dataofs=5L reserved=0L flags=PA window=4380 chksum=0xb718 urgptr=0 options=[] |<MyEthTrailer |<Padding load='\xPayload of MyEtherTrailer' |>>>>>> [UPDATE-1]
I can force decoding a TCP SYN packet by calling :
packet[TCP].decode_payload_as(MyEthTrailer) However, the bind_layers method, does not seem to work automatically, and this does not work with more complex packet because it's mixing up TCP Padding with MyEthTrailer payload.
[UPDATE-2]
I got it partly working, but every packet needs to be casted properly, then I can read the trailer payload and decode it. For example if a packet is TCP/DNS/MyEthTrailer, this will work. If I don't know it's DNS, and it's not set up properly, it's still mixed in in TCP payload and Padding.
Your help is appreciated.
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